This invention relates to wheel scale assemblies and load cell structures for weighing loads. Particularly, this invention relates to improved portable electronic wheel scales having predetermined load cell structures and arrangements to provide lightweight, low profile and accurate weighing scales.
A co-pending U.S. patent application entitled, "Low Profile Wheel Scale Assembly", Ser. No. 199,478 filed 5-27-88 by applicant Kroll has also been filed. That application further describes and claims low profile wheel scales which utilize the load cell structures of this invention.
Applicant has previously disclosed wheel scale and load cell assemblies in U.S. Pat. No. 4,714,121. The wheel scale assembly of this invention is of a lower profile, a different structure and also shows the use of new and improved load cell structures. Although the present load cells are also of the shear load cell type, they have different configurations and function with different cooperating wheel support plate structures.
Wheel scales or platform scales are commonly used to measure axle weight loads of vehicles, such as trucks. And, although some platform scale devices are designed to accommodate the multiple wheels of dual tandem rear axle assemblies of commercial trucks, most wheel scale devices have a single platform to measure the load from single or dual wheels.
In use, a pair of wheel scales are spaced apart and the vehicle is driven onto the scale platforms one axle at a time. Each axle weight load is recorded and the summation of axle weights yields the gross weight of the vehicle.
Wheel scales utilizing load cells for weighing axle loads of motor vehicles are known in the weighing art. Additionally, wheel scales which utilize strain gauge sensors fixed to deflectable load cells are known. However, the specific configuration of the load cells utilized in prior art scales, the placement of the load cells in the housing structures of these scales, and the cooperation of the active and inactive elements of these prior art wheel scale devices often yield complex and bulky wheel scales which are inaccurate and unrepeatable under many conditions of use.
For example, prior art wheel scale devices have been proposed and manufactured to use various types of load cell configurations for the purpose of yielding a lightweight, low profile and accurate portable wheel scale. Additionally, various wheel scale structures have been proposed and manufactured wherein these load cell configurations have been utilized with varying cooperative elements. However, these prior art wheel scale structures have often been difficult to transport and utilize, have been susceptible to damage, and have required the precise load placement of loads to achieve reasonable scale accuracy and repeatability.
Although load cell assemblies are usable in a variety of vehicle scale devices, there are specific requirements and difficulties associated with their use in portable wheel scales used by law enforcement officers, for example. Such portable wheel scales must be unitary, lightweight and rugged assemblies able to withstand the lateral forces resulting from the braking and skidding of truck tires.
Additionally, such portable wheel scales are preferably usable on a variety of road surfaces or terrains, should have low or thin profiles to prevent weighing inaccuracies caused by load shifts and are preferably accurate and reliable irrespective of precise wheel placement onto the platform structures. The load cell assemblies of this invention in conjunction and cooperation with the scale housing structure and load platform support structures provide such a low profile, reliable and accurate portable wheel scale.
Many types of load cell assemblies have been used or proposed for use in weighing scales as well as in portable wheel scales. And most such uses have required various load cell restraining and retention mechanisms. Depending upon configuration, these load cell fastening or restraining structures have often resulted in unreliable and unrepeatable load cell output. The load cell structures and wheel scale assemblies of this invention do not require the use of these load cell restraining mechanisms.
Despite the need for a truly portable, low profile, sturdy and accurate wheel scale device and load cell structures which overcome the problems associated with these prior art weighing scales and load cells, none in so far as is known, has been proposed or developed. Accordingly, it is the object of this invention to provide a lightweight, fully electronic, self contained, high capacity wheel load scale which has a low profile and which utilizes load cell structures and arrangements that provide for the accurate and repeatable weighing of loads under a broad range of environmental conditions.